The proposed research has as its goal the better understanding of human disease- and age-related otoconial loss by learning more about otoconial seeding, growth, and dissolution in exprimental animals, chiefly the rat. Important findings in the rat fetus indicate that organic material is essential to the genesis, growth and achievement of the adult configuration of otoconia. Thus, the biochemical nature and amino acid content of the organic material in the otoconia must now be determined by analytical methods. Radioautographic procedures to uncover the metabolic pathways of amino acids believed to be incorporated into the ontoconia and otolithic membranes, and to ascertain changes in composition or rate of turnover in old versus young animals, are being employed. Radioautography will be carried out transmission electron microscopically as well as at the level of the light microscope. Biochemical analytical and radioautographical findings are expected to shed new light on calcification processes in otoconia and to be relevant to understanding disease- and age-related vestibular dysfunctions, including cupulolithiasis, in man. With new insights into otoconial formation and the extent to which it can occur after birth, we should begin to learn whether or not prevention of otoconia loss or repair of demineralized crystals is possible.